This disclosure relates generally to the field of window displays. More particularly, this disclosure relates to collecting and displaying shadows associated with overlapping windows.
Many modern windows-based operating systems provide a user interface based on a “desktop” paradigm. These operating systems present information (text and graphics) to users through windows as displayed against, or on top of, a desktop. Often, each window casts a shadow as a visual aid to help the user distinguish spatially close or overlapping windows. In general, shadows are part of their corresponding window and are often pre-generated, being laid-down or rendered immediately before/beneath their corresponding window. In this approach regions in which shadows overlap are re-painted each time a shadow is rendered to that region. This leads to shadow areas that are too dark to mimic reality. This situation is illustrated in FIG. 1 in which three overlapping windows are shown: bottom window 100, middle window 105, and top window 110—each having its own shadow (each, separately, identical). As windows overlap so too do their shadows. In regions 115 and 120 only a single shadow has been rendered—these regions are the lightest shadow regions. Shadows have been rendered twice in regions 125 and 130 and in region 135 the shadows from all three windows overlap. As shown, regions 125 and 130 are darker than single-shadow regions 115 and 120, but lighter than triple-shadow region 135.